1. Field of the Invention
The present invention relates to a novel active electronic component which can operate at high speed and an electronic apparatus using the component.
2. Description of the Related Art
It is not easy to downsize silicon-made field effect transistors (Si transistors), which are currently used in communication circuits, logic circuits and the like, to the theoretically-predicted limit. There are a lot of problems in reducing in size an Si transistor for the purpose of enhancing the performance and improving the degree of integration.
For instance, when the Si transistor size is 100 nm or smaller, higher exposure and etching techniques are required, and in addition to these difficulties met in the manufacture process, such Si transistor has operational problems in short channel effect and temperature rise of the device. In the case of a logic device, the conduction effect below the threshold, output conductance, and device power gain are reduced. In the case of a volatile memory such as a dynamic random access memory and a non-volatile memory device such as an electrically-erasable programmable random access memory device, conduction below the threshold brings leakage of accumulated electric charges and lowering of the threshold performance.
On the other hand, transistors formed from new materials such as GaAs are difficult to process and can hardly build large-scale integrated circuits aside from some logic circuits and communication devices.
Recently, carbon nanotubes are attracting attention as new semiconductor materials. This is because carbon nanotubes are about 10 nm in diameter and have a conduction mechanism resembling ballistic conduction, which enables a carbon nanotube device to operate at high speed and causes the device to generate less heat.
Using single wall carbon nanotubes that exhibit the semiconductor characteristic, rectifiers and transistors have heretofore been manufactured by way of trial. An advantage of using a carbon nanotube as an electronic device resides in that the conduction mechanism of carbon nanotubes, namely, ballistic conduction, hardly allows electrons to scatter within a solid substance. In other words, transistors constructed from carbon nanotubes are advantageous in high speed operation and less heat generation of carbon nanotubes.
In addition, carbon nanotubes are suitable as a device and electrode of a minute circuit because general carbon nanotubes are about 1 to 20 nm in diameter. The technique of manufacturing devices using carbon nanotubes is making an advance, and available now are such techniques as separating single wall carbon nanotubes that exhibit the semiconductor characteristic from the carbon nanotubes that doesn't exhibit the semiconductor characteristic and doping a carbon nanotube with an impurity.
Several techniques related to devices that use carbon nanotubes have been disclosed. Examples of those techniques include one for building a field effect transistor that operates at room temperature by connecting to a platinum electrode a single wall carbon nanotube that exhibits the semiconductor characteristic (see S. J. Tans, et al., Nature, vol. 33, 1998, pp. 49–51, “Room-temperature transistor based on a single carbon nanotube”), and one for manufacturing a p-channel carbon nanotube transistor and an n-channel carbon nanotube transistor to build a complementary type inverter from the p-channel and n-channel transistors (see A. Javey et al., Nano Letters, vol. 2, 2002, pp. 929–932, “Carbon Nanotubes Transistor Arrays for Multistage Complementary Logic and Ring Oscilators”).
However, according to operation examples that have been reported so far, the oscillation frequency of a carbon nanotube transistor evaluated by a ring oscillator is about 200 Hz, meaning the operation speed is very slow. High storage capacitor of wiring is suspected as the cause of the slow operation speed. On the other hand, it is considered that ballistic conduction of the carbon nanotube hinders the carbon nanotube transistor from performing normal transistor operation.
Of carbon nanotubes, only single wall carbon nanotubes exhibit the semiconductor characteristic. Furthermore, not all of single wall carbon nanotubes exhibit the semiconductor characteristic and the rest show metallic properties. Multilayer carbon nanotubes show metallic properties while none of them exhibit the semiconductor characteristic. Only carbon nanotubes with the semiconductor characteristic can constitute normal active electronic devices that utilize field effect. Although there has been proposed a method in which each carbon nanotube receives a large amount of current to eliminate carbon nanotubes that exhibit metallic properties, thus leaving those with the semiconductor characteristic (see P. G. Collins, et al., Science, vol. 292, 706–709, “Engineering Carbon Nanotubes and Nanotube Circuits Using Electrical Breakdown”), the method requires troublesome manipulation and is not suitable for mass production.